1. Field of the Invention
The present invention pertains to vehicle wheel aligning apparatus, and more particularly, to a wheel-mounted aligner which uses a projected light beam and a target to determine an angle of the wheel from which the beam was projected.
2. Description of the Prior Art
In order to provide good performance of the steering portion of a motor vehicle and to promote tire life it is necessary that the front end of the vehicle be correctly aligned. To insure that the front end is correctly aligned, the accurate and rapid measurement of relatively small angles is necessary, and it is important that such measurements be made with a minimum of effort and calculation by the operator. It is also essential that the equipment being used can compensate for vehicles having widely different spacings between the wheels of the vehicle.
Various types of wheel aligning devices have heretofore been commercially utilized, and the present invention deals with apparatus wherein a projector is mounted upon one of the wheels to be aligned to project a beam having a predetermined known angular relationship with the axis of rotation of that wheel. The projected beam may be projected forwardly to fixed scales, or, in more recently developed wheel aligners, the beam may be projected across the vehicle to a "target" which is mounted upon the transversely adjacent vehicle wheel. This "target" may comprise a scale or an indicating means for indicating a predetermined angular relationship of the wheels, or, it may be comprised of a mirror merely reflecting the beam back to a scale or indicating means on the wheel from which the beam emanates. Examples of such types of wheel aligning devices are shown in U.S. Pat. No. 3,782,831 to Senften, issued on Jan. 1, 1974; U.S. Pat. No. 3,865,492 to Butler, issued on Feb. 11, 1975; U.S. Pat. No. 3,888,592 to Geul, issued on June 10, 1975; and U.S. Pat. No. 3,393,455 to MacMillan, issued on July 23, 1968.
In all of the aforedescribed prior art angular measuring devices for determining vehicle wheel alignment, a continuing problem exists with regard to obtaining the necessary accuracy of the measurements, such problem being compounded by the less than ideal garage conditions under which the measurements are typically made and by the frequent lack of necessary skill and/or training in the personnel making the measurements.